There have heretofore been known a servo press in which an eccentric rotation mechanism is driven by a servo motor and the rotating power of the eccentric rotation mechanism is transmitted to a slide through a toggle linkage thereby moving the slide up and down (e.g., Patent Document 1). Since this servo press is able to vertically move the slide at high speed by the continuous rotation of the servo motor, it can perform high-production industrial processing.
Another known servo press is configured such that the rotating power of the servo motor is converted into a substantially horizontal linear movement by a ball screw mechanism and this linear movement is in turn converted into a vertical movement by a toggle linkage to vertically move the slide (e.g., Patent Document 2). In this servo press, a conversion equation is prestored for calculating the substantial positional gain of a slide position obtained from a relational expression representative of the relationship between the position of the slide and the position of the ball screw or nut. During actual control of the slide, the positional gain is corrected according to the position of the slide, using the conversion equation for the substantial positional gain, and a motor speed command is calculated from the deviation of the position of the slide and the corrected positional gain to control the servo motor. This servo press is capable of accurately positioning the slide so that high-accuracy processing can be properly performed.
Patent Document 1:JP-A-2004-17098Patent Document 2:JP-A-2003-305599